... just found the solution myself.
It is part of the background settings in KDE4.

HOW-TO:
right click on the desktop background.
there is a context menu entry like 'Settings ..' (I run German localization - just a fuzzy translation ;-))
Within this setting dialog popping up you can choose a type like slide show.

Some more cool types are available as well like marble and the weather ...

I've now tried in on 4 systems, 1 was a laptop, another a 32bit workstation, yet another was a 64-bit workstation and the last a Virtualbox (32bit) installs of Ubuntu 9.10. All failed to start with the same problem as stated above.